The present invention is directed to a contactless communication system having a high bit rate contactless data transfer.
FIG. 7 illustrates a known contactless communication system 700. The basic components of contactless communication system 700 are a reader 710 and a contactless card 720.
The reader 710 is also known as a Proximity Coupling Device (PCD). The reader 710 includes generator voltage U0, transmission antenna LPCD, resonance capacitor Cres, and resistor RQ. Transmission antenna LPCD and resonance capacitor Cres are configured to be in resonance, such that at a predetermined frequency, only resistor RQ is seen from the perspective of the generator voltage U0.
The contactless card 720 is also known as a Proximity Integrated Circuit Chip (PICC), a smart card, a tag, a transponder, or a Radio Frequency Identification (RFID) tag. Contactless card 720 includes an inductive antenna LPICC, resonance capacitor CPICC, and power consuming resistor RPICC. Antenna LPICC and resonance capacitor CPICC form a resonance circuit, and are configured to provide contactless card 720 with a specific resonance frequency.
In operation, transmission antenna LPCD transmits a carrier signal, typically having a frequency of 13.56 MHz, which generates a transmission field to supply the contactless card 720 with power and data. Data can be transmitted to contactless card 720 by amplitude modulation of the carrier signal. When the contactless card 720 penetrates the transmission field of the reader 710, the transmission field induces a current in card antenna LPICC. A voltage corresponding to the induced current is then multiplied by the resonance circuit. The contactless card 720 is configured to transmit a response signal, which is provides as the carrier signal with data modulated on a subcarrier frequency, typically at a frequency of 848 KHz. The response signal generates a response field that is detected by the transmission antenna LPCD of reader 710.
In known systems such as contactless system 700, the communication protocol between the reader and the contactless card may be defined by any of numerous ISO (International Organization for Standardization) standards, such as 14443 Type A/B/C, 15693, 18000, etc.
Furthermore, the contactless communication system 700 is described as having downlink and uplink communication. The downlink communication is the transferring of data, and possibly power, from the reader 710 to the contactless card 720, while the uplink communication is the transferring of data from the card 720 to the reader 710.
To optimize energy transfer during downlink communication from the reader 710 to the contactless card 720, the reader's high-Q resonance circuit, comprising resonance capacitor Cres and transmission antenna LPCD focuses on the carrier frequency. The resulting bandwidth is low, and subfrequencies carrying data transmitted to contactless card 720 as well as data transmitted back from contactless card 720 are attenuated.
To speed up data communication in the uplink direction, the subcarrier frequencies carrying data are increased. Since the reader's high-Q resonance circuit attenuates subcarrier frequencies, optimizing energy transfer in the known contactless communication systems therefore has had a negative impact on data transfer.